1. Field of the Invention
The present invention relates to a system, method and apparatus for the conversion of coal into liquid and gaseous products by microbiol solubilization. More specifically, the present invention relates to a fluidized-bed bioreactor system capable of continually and economically producing liquid and gaseous coal products by microbial solubilization.
2. Description of Related Art
Conventional, thermal and chemical processes for the conversion of coal to liquid and gaseous products generally require somewhat extreme temperature, pressure, and chemical conditions. The severity of the operating conditions may commonly include pressures in excess of 3000 psi and temperatures in excess of 800.degree. F. These processes also usually require a significant capital investment. Because of the relatively mild operating conditions associated with many biological processes, there has been a recurring interest in the potential use of microorganisms for coal processing.
There have been earlier suggestions that microorganisms may be able to solubilize native coal. M. H. Rogoff et al, Microbiology of Coal, U.S. Bureau of Mines, Information Circular 8075 (1962); J. A. Korburger, 36 Proc. W. Va. Acad. Sci. 26 (1964). In recent experiments, certain strains of fungi have been shown to produce a liquid product when cultured on the surface of lignite coal in the presence of humid air. M. S. Cohen and P. O. Gabrielle, 44 Appl. Environ. Microbiol. 23 (1982); C. D. Scott, G. W. Strandberg, and Susan N. Lewis, 2 Biotech. Progress, 161 (1986). Although the scientific feasibility of microbial solubilization of coal is currently being established, up to this time it has not been reported that large-scale bioreactor concepts or continuous bioreactor production methods are feasible.
It has also been found that although a variety of fungal species have been shown to be able to form liquid products from coal, only one highly oxidized North Dakota lignite coal has been found to be susceptible to both rapid (1-3 days) and extensive liquefaction (about 80-90% of solids solubilized). Other coals and have been found to give sporatic evidence of limited liquefaction.
It is therefore desirable to scale-up laboratory techniques which employ suspension cultures of microorganisms that interact with coal into processes which provide for the microbial solubilization of coal in an efficient and economical manner. It is further desirable to carry out coal microbial conversion processes which allow for the continuous production of liquid and gaseous products at minimal costs.
It is still further desired to increase the susceptibility of lignite and subbituminous coals to microbial liquefaction and to reduce the time period required for microbial liquefaction.